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Home > Education > Activities and Resources for Earth Science Teachers > Activity #5
Activity #5: A Percolation Revelation
To relate the rate at which water moves through various types of ground materials to the mechanical aspects of cleaning up a pollution spill situation.
Two 45 minute periods.
As water enters and moves through a soil, it becomes available to the plant roots and animals which exist in that soil. The speed at which the water passes through the soil determines how long it is available and how much is present for use by the soil organisms. Many physical and chemical factors of the soil have a significant effect on the percolation rate, and a complete soil analysis would be necessary to isolate each of these factors. If a pollutant is introduced into the water, or spread on the surface of the soil, this pollutant will be carried into the soil with the water and thereby will reach the plants and animals. The percolation ability of a soil not only indicates the rate at which the pollutant reaches the soil organisms, but will also affect the rate at which the pollutant may be flushed or leached from the site.
A great number of human activities hold the potential for creating pollution of soils and the ground water held in those soils. Underground and aboveground storage tanks, septic systems, sludge and ash, pesticides, fertilizers, herbicides, and air pollutants, all pose threats to the soils and ground water of the country.
Students should work in groups of two or three. Each group will need three (3) half-gallon paper milk cartons, a nail, three 400 ml beakers, a water supply, a graduated cylinder, a stopwatch or clock with a second hand, a grease pencil, a ruler, samples of dry fine gravel, sand, and topsoil, and a few drops of food coloring. Each individual student will need a notebook and pens.
Cut off the tops of the milk cartons, leaving about 6 inches remaining; use the nail to poke a hole in ONE CORNER of the carton bottom from the inside. Fill the cartons to a depth of one inch with the materials to be tested; one type per carton. Place each carton on top of a 400 ml beaker with the drain hole down. See Figure 1 on the student sheet. Mark the catch beakers up one inch from the bottom with the grease pencil and slowly add 250 ml of water to each carton. Have students record the data and perform the indicated calculations. See data tables.
To test pollution flushing on the three samples have students repeat steps 1-4 (see student sheet). Add several drops of a brightly colored food coloring to the 250 ml of water and add this volume to each of the samples. Allow most of the water to pass through the sample. Empty and clean the catch beakers and replace them beneath the cartons. Add clean water, 50 ml at a time, to the samples until the water draining through runs clear. Record the volume of clean water needed to flush each sample.
SPECIAL SAFETY PRECAUTIONS
Have students research and discuss other methods of removing pollutants from a contaminated area.
Have students search newspaper files and magazine articles to determine how Exxon "cleaned up" the Valdez oil spill.
Have students explain why water holding capacity and percolation rate should be considered when sites are chosen for solid waste disposal or radioactive waste disposal.
Have students do Activities #3 (Ground Water and Development Siting) and #4 (Water, Water, Everywhere; and not a Drop to Drink!) which deal with the related aspects of building codes and site proposals for single family house construction.
Have students conduct a Household Contaminants Inventory of their own home and list all the things and the quantities involved that could become ground water/soil contaminants if used improperly.
Activity developed by James H. Barden, in conjunction with the 1991 CREST intern program.
Activity #5: A Percolation Revelation
To relate the percolation rate of a soil type to the mechanical aspects of pollution cleanup.
Each group of students will need the following: three (3) one-half gallon cardboard milk cartons, a nail, three (3) 400 ml glass beakers, a water supply, a graduated cylinder, a stopwatch or clock with a second hand, grease pencil, ruler, samples of dry fine gravel, sand, and topsoil, food coloring. Each student will need their pens and notebook.
PART I. The first part of the exercise will give you some background on the rate at which water moves through different types of soil. This rate is called the percolation rate. It is important to know the percolation rate of various soil types before studying how pollutants move through the soil.
PART II. In this part you will test the three samples to see how quickly they will allow a pollutant (food coloring in the water) to be flushed out of them.
1. Which sample had the fastest percolation rate?
2. Which sample was the easiest to clean?
3. Is there a relationship here? Explain.
4. Which sample had the greatest holding capacity?
5. Was the sample in question four the hardest to clean? Explain.
Last updated on October 6, 2005
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